Suture-needle combination with cyanoacrylate tipped sutures

ABSTRACT

A method and apparatus for tipping surgical sutures which includes winding the suture around a drum while continuously monitoring the suture diameter in x and y directions and adjusting the tension on the suture to control the suture diameter as it is being wound. The drum is then placed in an apparatus which passes selected portions of the suture through a mist of cyanoacrylate tipping agent generated by ultrasonic atomization. The tipping agent quickly cures and the tipped portion of the suture may be cut to create a tipped end for insertion into a surgical needle to form a needle suture device.

This application is a divisional of U.S. application Ser. No. 08/007,361filed Jan. 21, 1993, now U.S. Pat. No. 5,269,808, which is acontinuation of U.S. application Ser. No. 07/626,995, now abandoned,filed Dec. 13, 1990.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a tipped surgical suture and a method andapparatus for making same and a combined tipped suture and surgicalneedle. In particular, it relates to a cyanoacrylate tipping agent forbraided sutures to prevent brooming and to increase stiffness, therebyfacilitating attachment of the suture to a surgical needle.

2. Background of the Art

For many years, surgeons have employed needle-suture combinations inwhich a suture or ligature is attached to the shank end of a needle.Such needle-suture combinations are provided for a wide variety ofmonofilament and braided suture materials, both absorbable andnon-absorbable, e.g., catgut, silk, nylon, polyester, polypropylene,linen, cotton, and absorbable synthetic materials such as polymers andcopolymers of glycolic and lactic acid.

Needle-suture combinations fall into two general classes: standard, ornon-detachable, needle attachment and removable, or detachable, needleattachment. In the case of standard needle attachment, the suture issecurely attached to the needle and is not intended to be separabletherefrom, except by cutting or severing the suture. Removable needleattachment, by contrast, is such that the needle is separable from thesuture in response to a force exerted by the surgeon. Minimum acceptableforces required to separate a needle from a suture (for various suturesizes) are set forth in the United States Pharmacopoeia (USP). As todetachable needles, the United States Pharmacopoeia prescribes minimumindividual pull-out forces and minimum average pull-out forces asmeasured for five needle-suture combinations. The minimum pull-outforces for both standard and removable needle-suture attachment setforth in the United States Pharmacopoeia are hereby incorporated byreference.

One typical method for securing a suture to a needle involves providinga cylindrical recess in the shank end of a needle and securing a suturetherein. For example, U.S. Pat. No. 1,558,037 teaches the addition of acement material to such a substantially cylindrical recess to secure thesuture therein. Additional methods for bonding a suture within a needlebore are described in U.S. Pat. Nos. 2,928,395 (adhesives) and 3,394,704(bonding agents). Alternatively, a suture may be secured within an axialbore in a needle by swaging the needle in the region of the recess. See,e.g., U.S. Pat. No. 1,250,114. Additional prior art methods for securinga suture within a needle bore include expansion of a catgut suturethrough the application of heat (U.S. Pat. No. 1,665,216), inclusion ofprotruding teeth within the axial bore to grasp an inserted suture (U.S.Pat. No. 1,678,361) and knotting the end of the suture to be insertedwithin the bore to secure the suture therein (U.S. Pat. No. 1,757,129).

Methods for detachably securing a suture to a needle are also wellknown. For example, U.S. Pat. Nos. 3,890,975 and 3,980,177 teach swaginga suture within a needle bore such that the suture has a pull-out valueof 3 to 26 ounces. Alternative detachable attachment methods includeproviding a weakened suture segment (U.S. Pat. No. 3,949,756), lubricanttipping the end of a suture to be inserted in the axial bore of a needle(U.S. Pat. No. 3,963,031) and pre-tensioning a suture that is swagedwithin an axial needle bore (U.S. Pat. No. 3,875,946). See also, U.S.Pat. Nos. 3,799,169; 3,880,167; 3,924,630; 3,926,194; 3,943,933;3,981,307; 4,124,027; and, 4,127,133.

Another method for attaching a suture to a needle involves the use oftubing which is secured to the shank end of the needle and to thesuture. For example, U.S. Pat. No. 1,613,206 describes the use of atubing (preferably silver)i which is secured to the shank end of aneedle and to a ligature. It is suggested that the tube may be attachedto the needle by pressure or soldering and to the ligature by pressureor cementing. It is also suggested that the shank of the needle be ofreduced cross section and that the furthest extremity of the reduceddiameter shank section be provided with a spike or point upon which thesuture may be secured prior to tube application.

U.S. Pat. No. 2,240,330 describes a tubing attachment method whereby thetubing and suture are releasably secured to the needle. In particular,the needle and tubing are provided with cooperating catch and abutmentmeans which are released one form the other by rotating the needle 90°relative to the tubing (or vice versa). The tubing is manufactured fromspring-tempered carbon steel or chrome nickel steel and is secured tothe suture by heating the tubing and then swaging to the suture.

U.S. Pat. No. 3,311,100 related to a flexible composite suture having atandem linkage. The needle is secured to a flexible suture leadermanufactured from a readily sterilizable plastic such as nylon, linearpolyethylene, isostatic polypropylene, polyester, silk or otherproteinaceous material, e.g., by inserting and crimping the leaderwithin an axial bore in the needle shank. The opposite end of the sutureleader is crimped within a connector sleeve of a thin walled metaltubing, e.g., stainless steel. The opposite end of the tubing is crimpedaround a steel suture, e.g., monofilament stainless steel.

U.S. Pat. No. 3,918,455 describes a needle-suture attachment wherein ahollow suture portion is secured to the shank end of a needle which isof reduced cross-section as compared to the remainder of the needle.

Additional patents which describe the use of tubing to effectsuture-needle attachment include U.S. Pat. Nos. 4,672,734 (formingneedle from U-shaped metal plate round suture), 4,359,053 (siliconetubing), 3,835,912 (laser welding of metal tube to needle), 2,814,296,2,802,468 (Chamfered tubing ends), 2,302,986, 2,240,330, 1,981,651(needle and tubing screw threaded), 1,960,117, and 1,591,021.

In addition to the needle-suture constructions of the aforedescribedpull-out variety, it is known from U.S. Pat. No. 4,805,292 to provide aneedle-suture combination in which a suture cutting edge is formed atthe shank end of the needle. However, the combined needle-suture deviceof U.S. Pat. No. 4,805,292, like others described above, possesses asuture tip-receiving axial bore, or recess, formed-in the butt end ofthe needle and as such is subject to the disadvantages recounted abovewhich are associated with a needle possessing an axial bore.

Insertion of sutures into a hole, recess or tube for attachment tosurgical needles presents problems peculiar to suture needlecombinations. Braided multifilament sutures in particular are difficultto insert into the very small aperture of a surgical needle: unlessmodified, they are too limp for the suture tip to be controlled forinsertion and they have a tendency to "broom" i.e., the filaments have atendency to flare out at the cut end so that the diameter of the cut endexceeds the diameter of the needle hole. Various techniques have beenemployed to modify sutures to overcome the problems of limpness andbrooming. One known method employs a tipping agent, which is a materialused to coat the suture to stiffen the filaments and adhere themtogether.

Typically, a suture to be tipped is first placed under tension to reduceslack so that the suture may be maintained in a predetermined positionon a frame or rack or other suture holding device. Optionally, thetension may be such as to reduce the diameter of the suture. SeeCanadian Patent Nos. 1,009,532. The suture is then dipped into thetipping solution and allowed to dry while under tension. The sutures arethen dried, such as by being warmed in a drying oven at about 225° F.for about 10 minutes. After drying the sutures can be cut and releasedfrom tension. The process results in a tipped end on each side of a cut.Where tension has optionally been employed to reduce the suturediameter, release of said tension will allow the suture to expand to itsoriginal diameter except at the tipped end portion This can facilitateinsertion of the end into a needle

Tipping agents may be dissolved in solvents to form dipping solutions.By way of example, Mariotte mixture is a dipping solution comprisingnylon dissolved in isopropyl alcohol. Other polymers and solvents mayalso be used. Gould mixture is a dipping solution comprising nylondissolved in methanol. At least one major manufacturer of surgicalneedles recommends use of Mariotte mixture or Gould mixture for tippingsutures. A multitude of other tipping agents, including polymers andsolvents, have been proposed. For example McGregor U.S. Pat. No.3,890,975 discloses coating the suture with a binding resin or adhesive.The composition may be any non-toxic adhesive composition, eitherorganic, inorganic or a hybrid. Suitable organic materials are suchnatural products as starch, dextrin, asphalt, animal and vegetableproteins, natural rubber, shellac, semi-synthetic products such ascellulose nitrate and the other cellulosics, polyamides derived fromdimer acids, castor-oil based polyurethanes; such well-known syntheticresins as vinyl-type addition polymers, both resins and elastomers;polyvinyl acetate, polyvinyl alcohol, acrylics, unsaturated polyesters,butadiene/acrylonitrile, butadiene/styrene, neoprene, butyl rubber,polyisobutylene; and polymers formed by condensation and other step-wisemechanisms, i.e., epoxies, polyurethanes, polysulfide rubbers, and thereaction products of formaldehyde with phenol, resorcinol, urea, andmelamine. McGregor states that particularly preferred bondingcompositions are epoxide resins and polyester resins.

Schmitt U.S. Pat. No. 3,736,646 discloses that it is known to tipbraided sutures by dipping the end of the suture in a plastic such as asolution in isopropyl alcohol. Schmitt suggests that for absorbablesutures an absorbable tipping agent is desirable, and proposes that acopolymer of lactic and glycolic acid dissolved in a suitable organicsolvent, such as xylene or toluene, be applied to tip the suture.

Nichols U.S. Pat. No. 2,734,506 discloses a dipping solution of polymersof methacrylic acid esters in an organic solvent such as toluene, xyleneacetone, ethyl acetate, methylethyl ketone, or naphtha.

Shepherd et al. U.S. Pat. No. 3,849,185 discloses the use of an acryliccasting syrup as a tipping agent, the syrup being fully polymerizedafter being applied to the suture.

In addition, paraffin/hexane solution (10% paraffin) has been used as asuture coating agent as well as Arrochem (TM), a nylon resin plusmethanol composition manufactured by ArroChem,. Inc. of 201 WestlandFarm Road, Mt. Holly, N.C. 28120, and SILASTIC (TM) Medical Adhesive (asilicon elastomer composition manufactured by Dow Corning Co.

Although dipped sutures prepared in accordance with the above proceduresmay have been used successfully, there are several drawbacks with theuse of tipping solutions. The main problems relate to tippingconsistency and process control. Non-uniform solvent evaporation, whichmay be caused by variations in the solvent, oven temperature and heatingtime can result in inconsistent tipping. Furthermore, the dried residueof polymer left after evaporation can flake off or develop cracks.

Another method which has been employed for treating sutures involvesmelt fusion, as described in U.S. Pat. No. 4,832,025, issued to Coates.The suture is heated to a temperature at least high enough to "meltfuse" a portion of the outer filaments of the suture. According toCoates, such temperature is typically about 260° C. to 300° C. (500° F.to 572° F.). Exposure of synthetic sutures to such extreme temperaturesmelt fuses the filaments, and the melt fused suture portion stiffensupon cooling. Melting of the filaments has the effect of holding thefilaments together when the suture is cut. It also causes stiffening ofthe suture which facilitates insertion of the suture end into thedrilled hole of a needle. However, the melt fusion of suture hassignificant drawbacks.

Firstly, the melt fusion of filaments weakens the suture, whose tensilestrength is degraded in proportion to the extent of melt fusion.

Secondly, melt fusion causes an irreversible change in the filamentswhich result in permanent stiffening and permanent loss of tensilestrength.

Thirdly, with the extreme temperatures disclosed by Coates for meltfusion an inconveniently short heating cycle is required. For example,for a size 3/0 silicone coated polyester suture heated to between 260°C. to 300° C. in a 4 mm. diameter heating tunnel, the heating time is nomore than about 3 seconds. Such short heating times make it difficult tocontrol the process and leads to inconsistencies and variations in themelt fused tipping process.

A further consideration pertinent to suture tipping is that sutures areoften prepared with lubricant coatings such as silicone or fatty acidsalts in order to increase lubricity and to improve "tie-down"performance, i.e., the ease of sliding a knot down the suture intoplace. Such lubricant coatings typically are incompatible with thematerials and methods currently employed for tipping sutures. Inparticular, prior known tipping agents do not adhere well to lubricantcoated sutures, which may result in inconsistent tipping or anundesirable reduction of suture-needle pull out force. The melt fusingmethod of tipping may destroy the lubricant coating or render it lesseffective in areas away from the needle.

A method of and apparatus for tipping surgical sutures has beendiscovered which may be used to tip both uncoated and coated sutures andwhich provides superior stiffening of the suture for insertion into anopening to attach the suture to a needle.

SUMMARY OF THE INVENTION

A surgical suture tipped with cyanoacrylate and a process for tippingwith cyanoacrylate are disclosed. In addition, a method and apparatusare provided herein for handling and tipping a surgical suture.

In the preferred embodiment a suture is wound around a drum while itsdiameter is continuously monitored in the x and y directions, with thetension on the suture continuously being adjusted to consistentlycontrol the diameter of the suture as it is wound onto the drum. Thedrum is then placed in an apparatus which passes selected portions ofthe suture through a mist of cyanoacrylate tipping agent generated bysonic or ultrasonic atomization. The tipping agent quickly cures as itpolymerizes in response to ambient residual moisture to stiffen thecoated portion of the suture. The coated portion of the suture may becut to create at least one tipped end for insertion into a surgicalneedle. To assure consistent repeated processing the atomizationapparatus is flushed before and after each cycle with nitrogen in orderto prevent curing of the cyanoacrylate in the apparatus, which wouldundesirably interfere with proper operation of apparatus.Advantageously, cyanoacrylate tipping in accordance with the inventioncan be used effectively to tip all types of sutures, including filledsutures and sutures coated with lubricants and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway side view illustrating a surgical needleand suture combination.

FIG. 2 is an exploded perspective view illustrating a surgical needle inconjunction with a suture.

FIG. 3 is a partially cutaway side view illustrating a surgical needlein combination with a suture.

FIG. 4 is a diagrammator illustration of the suture winding system ofthe present invention.

FIG. 5 is a side elevational view of the suture winding apparatus of thepresent invention.

FIG. 6 is a perspective view of the suture winding drum of the presentinvention.

FIG. 6A is an end view of a rib configuration associated with the suturewinding drum.

FIGS. 6B and 6C show end elevational views of drums having 2 and 3notches, respectively.

FIG. 7 is a side view of the suture retaining clamp of the presentinvention.

FIG. 8 is a perspective view of the main support of the suture clamp.

FIG. 9 is a perspective view of the dowel arm support of the presentinvention.

FIG. 10 is a perspective view of the dowel arm of the present invention.

FIG. 11 is a perspective view of the rocker clamp support of the presentinvention.

FIG. 12 is a perspective view of the rocker clamp of the presentinvention.

FIG. 13 is a perspective view of the rocker spring of the presentinvention.

FIG. 14 is a perspective view of the suture tipping apparatus of thepresent invention.

FIG. 15 is a cut away front elevational view of the suture tippingapparatus of the present invention.

FIG. 16 is a cut away side elevational view of the suture tippingapparatus of the present invention.

FIG. 17 is a front sectional view of the spray head assembly of thesuture tipping apparatus.

FIG. 18 is a partially cut away side view of the spray head assembly ofthe suture tipping apparatus.

FIG. 19 is a perspective view of a suture with a tipped portion.

FIG. 20 is a schematic illustration of the suture tipping system of thepresent invention.

FIG. 21 illustrates the placement of clamps on the drum to secure thesuture for a cutting procedure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is generally directed to tipping surgical sutureswith cyanoacrylate in order to stiffen the suture tip and, as tomultifilament sutures, prevent brooming. Tipping the suture withcyanoacrylate facilitates insertion of the suture tip into an openingfor attachment to a suture. Advantageously, the cyanoacrylate tipping iscompatible with a broad range of sutures and coatings, and a novelmethod and apparatus have been developed for applying cyanoacrylate tosutures in an atomized spray. Because the cyanoacrylate tipping agentand process are applicable to a wide range of materials and needlesuture attachment methods, suture constructions and general methods oftipping sutures will be discussed prior to discussing the preferredapparatus for spray tipping.

The Suture

The present invention is primarily directed to the treatment of braidedsurgical sutures. The term "braid" means a substantially symmetricalstrand formed by crossing a number (at least three) of individualstrands composed of one or more filaments diagonally in such manner thateach strand passes alternatively over and under one or more of theothers. The braid may be of traditional tubular braid construction orspiroid braid construction and may include a core section composed ofone or more filaments around which the braid is externally fabricated.

The braided suture can be fabricated from a wide variety of natural andsynthetic fibrous materials such as any of those heretofore disclosedfor the construction of sutures. Such materials include non-absorbableas well as partially and fully bio-absorbable (i.e., resorbable) naturaland synthetic fiber-forming polymers. Non-absorbable materials which aresuitable for fabricating braided sutures include silk, polyamides,polyesters such as polyethylene terephthalate, polyacrylonitrile,polyethylene, polypropylene, silk cotton, linen, etc. Carbon fibers,steel fibers and other biologically acceptable inorganic fibrousmaterials can also be employed. Bio-absorbable sutures may be fabricatedfrom natural collagenous material or synthetic resins including thosederived from glycolic acid, glycolide, lactic acid, lactide, dioxanone,polycaprolactone, epsilon-caprolactone, trimethylene carbonate, etc.,and various combinations of these and related monomers. Sutures preparedfrom resins of this type are known in the art.

Braided multifilament sutures typically are coated with one or morecoating compositions to improve functional properties such as surfacelubricity and knot tie-down behavior. A variety of suture coatingcompositions proposed for either or both of these purposes are wellknown in the art, .e.g., those disclosed in U.S. Pat. Nos. 3,867,190;3,942,532; 4,047,533; 4,452,973; 4,624,256; 4,649,920; 4,716,203; and4,826,945.

A preferred lubricant coating is a bioabsorbable coating compositionobtained by copolymerizing in accordance with known procedures (1) apolyether glycol selected from the group consisting of relatively lowmolecular weight polyalkylene glycol, e.g., one corresponding to thegeneral formula HO(RO)_(y) H wherein R is an alkylene group of from 2-4carbon atoms and y is an integer of from about 100-350, and polyethyleneoxide-polypropylene oxide block copolymer, e.g., one corresponding tothe general formula H(OCH₂ CH₂)_(x) (OC₃ H₆)_(y) (OCH₂ CH₂)_(z) OHwherein x is,an integer of from about 45-90, y is an integer of fromabout 60-85 and z is an integer of from about 45-90 with (2) a mixtureof lactide monomer and glycolide monomer or a preformed copolymer oflactide an glycolide, the weight ratio of (1) to (2). preferably rangingfrom about 4:1 to about 1:4 and more preferably from about 2:1 to about1:2. The ratio of lactide to glycolide in the monomer mixture or in thecopolymer of these monomers preferably varies from about 65-90 molepercent lactide and 10-35 mole percent glycolide. Polyether glycolshaving molecular weights of about 3,500-25,000 and preferably from about4,000-10,000 and polyethylene oxide-polypropylene oxide block copolymershaving molecular weights of from about 4,000-10,000 and preferably fromabout 7,500 to about 9,000, e.g., those disclosed in U.S. Pat. Nos.2,674,619, 3,03,118, 4,043,344 and 4,047,533 and commercially availableas they Pluronics (BASF-Wyandotte). Where preformed copolymers oflactide and glycolide are employed in preparing the bioabsorbablecoating compositions, they may be prepared as described in U.S. Pat. No.4,523,591.

The amounts of bioabsorbable coating composition to be applied to thesuture, e.g., by coating, dipping, spraying or other appropriatetechniques, will vary depending upon the specific construction of thesuture, its size and the material of its construction. In general, thecoating composition applied to an unfilled suture will constitute fromabout 1.0 to about 3.0 percent by weight of the coated suture, but theamount of coating add on may range from as little as about 0.5 percent,by weight, to as much as 4.0 percent or higher. For a preferred filled(i.e. containing a storage stabilizing agent) braided suture, amounts ofcoating composition will generally vary from about 0.5% to about 2.0%with as little as 0.2% to as much as 3.0%. As a practical matter and forreasons of economy and general performance, it is generally preferred toapply the minimum amount of coating composition consistent with goodsurface lubricity and/or knot tie-down characteristics and this level ofcoating add on is readily determined experimentally for any particularsuture.

Recently it has been proposed to also apply to an absorbable braidedsuture a storage stabilizing amount of a filler material containing atleast one water soluble liquid polyhydroxy compound and/or esterthereof. In addition to having an enhanced degree of storage stability,a braided suture which has been filled with a storage stabilizing amountof, e.g., glycerol, exhibits better flexibility and "hand"characteristics than the untreated suture. Moreover, since thepolyhydroxy compounds are generally capable of dissolving a variety ofmedico-surgically useful substances, they can be used as vehicles todeliver such substances to a wound or surgical site at the time thesuture is introduced into the body.

The useful storage stability agents are generally selected from thewater soluble, liquid polyhydroxy compounds and/or esters of suchcompounds, preferably those having no appreciable toxicity for the bodyat the levels present. The expression "liquid polyhydroxy compound"contemplates those polyhydroxy compounds which in the essentially purestate are liquids, as opposed to solids, at or about ambienttemperature, e.g., at from about 15° C. to about 40° C. The preferredpolyhydroxy compounds possess up to about 12 carbon atoms and where theesters are concerned, are preferably the monoesters and diesters. Amongthe specific storage stabilizing agents which can be used with generallygood results are glycerol and its mono- and diesters derived from lowmolecular weight carboxylic acids, e.g., monoacetin and diacetin(respectively, glyceryl monoacetate and glyceryl diacetate), ethyleneglycol, diethylene glycol, triethylene glycol, 1,3-propanediol,trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, andthe like. Glycerol is especially preferred. Mixtures of storagestabilizing agents, e.g., sorbitol dissolved in glycerol, glycerolcombined with monoacetin and/or diacetin, etc., are also useful.

To prevent or minimize run-off or separation of the storage stabilizingagent from the suture, a tendency to which relatively low viscositycompounds such as glycerol are especially prone, it can be advantageousto combine the agent with a thickener. Many kinds of pharmaceuticallyacceptable non-aqueous thickeners can be utilized includingwater-soluble polysaccharides, e.g., hydroxypropyl methycellulose(HPMC), and the other materials of this type which are disclosed inEuropean Patent Application 0 267 015 referred to above, polysaccharidegums such as guar, xanthan, and the like, gelatin, collagen, etc. Anespecially preferred class of thickeners are the saturated aliphatichydroxycarboxylic acids of up to about 6 carbon atoms and the alkalimetal and alkaline earth metal salts and hydrates thereof. Specificexamples of such compounds include salts of lactic acid such as calciumlactate and potassium lactate, sodium lactate, salts of glycolic acidsuch as calcium glycolate, potassium glycolate and sodium glycolate,sales of 3-hydroxy propanoic acid such as the calcium, potassium andsodium salts thereof, salts of 3-hydroxybutanoic acid such as calcium,potassium and sodium salts thereof, and the like. As stated hereinabove,hydrates of these compounds can also be used. Calcium lactate,especially calcium lactate pentahydrate, is a particularly preferredthickener.

When a thickener is utilized, it will be incorporated in the fillingcomposition in at least that amount required to increase the overallviscosity of the storage stabilizing agent to the point where the agentno longer readily drains away from the suture in a relatively shortperiod. In the case of a preferred storage stabilizing agent-thickenercombination, namely, glycerol and calcium lactate, the weight ratio ofglycerol to calcium lactate can vary from about 1:1 to about 10:1 andpreferably is from about 6:1 to 8:1.

If necessary or desirable, the storage stabilizing agent together withoptional thickener can be dissolved in any suitable non-aqueous solventor combination of solvents prior to use. To be suitable, the solventmust (1) be miscible with the storage stabilizing agent and optionalthickener, if present (2) have a sufficiently high vapor pressure to bereadily removed by evaporation, (3) not appreciably affect the integrityof the suture and (4) be capable of wetting the surface of the suture.Applying these criteria to a preferred storage stabilizing agent,glycerol, advantageously in admixture with a preferred thickener,calcium lactate, lower alcohols such as methanol and ethanol areentirely suitable solvent carriers. When a solvent is utilized in thepreparation of the stabilizing agent, e.g., methanol, such solvent canbe employed in amounts providing a solution concentration of from about20% to about 50%, preferably about 30% to about 45%, by weight of thestorage stabilizing agent including any optional thickener.

As stated, a braided suture may be impregnated with one or moremedico-surgically useful substances, e.g., those which accelerate orbeneficially modify the healing process when the suture is applied to awound or surgical site. So, for example, the braided suture herein canbe provided with a therapeutic agent which will be deposited at thesutured site. The therapeutic agent can be chosen for its antimicrobialproperties, capability for promoting wound repair and/or tissue growthor for specific indications such as thrombosis. Antimicrobial agentssuch as broad spectrum antibiotics (gentamicin sulphate, erythromycin orderivatized glycopeptides) which are slowly released into the tissue canbe applied in this manner to aid in combating clinical and sub-clinicalinfections in a surgical or trauma wound site.

To promote wound repair and/or tissue growth, one or more biologicallyactive materials known to achieve either or both of these objectives canbe applied to the braided suture of the present invention. Suchmaterials include any of several Human Growth Factors (HGFs), magainin,tissue or kidney plasminogen activator to cause thrombosis, superoxidedismutase to scavenge tissue damaging free radicals, tumor necrosisfactor for cancer therapy, colony stimulating factor, interferon,interleukin-2 or other lymphokine to enhance the immune system, and soforth.

The filling composition can contain one or more additional componentswhich promote or enhance the wound healing effectiveness of the HGFcomponent. Thus, e.g., site-specific hybrid proteins can be incorporatedin the filling composition to maximize the availability of the HGF atthe wound site and/or to potentiate wound healing. See e.g., Tomlinson(Ciba-Geigy Pharmaceuticals, West Sussex, U LK.), "Selective Deliveryand Targeting of Therapeutic Proteins", a paper presented at a symposiumheld Jun. 12-14, 1989 in Boston, Md, the contents of which areincorporated by reference herein. The HGFs can also be associated withcarrier proteins (CPs), e.g., in the form of CP-bound HGF(s), to furtherenhance availability of the HGF(s) at a wound site as disclosed in"Carrier Protein-Based Delivery of Protein Pharmaceuticals", a paper ofBioGrowth, Inc , Richmond, Calif. presented at the aforementionedsymposium, the contents of said paper being incorporated by referenceherein. The HGFs can also be incorporated in liposomes to provide fortheir release over an extended period. Lactate ion can be present toaugment the wound healing activity of the HGF. Protectants for the HGFcan also be utilized, e.g., polyethylene glycols, acetoxyphenoxypolyethoxy ethanols, polyoxyethylene sorbitans, dextrans, albumin,poly-D-alanyl peptides and N-(2-hydroxypropyl)-methacrylamide (HPMA).

Cyanoacrylate Tipping

As stated previously, prior known tipping methodologies are not fullycompatible with a suture or its coatings, fillers, therapeutic agents,antimicrobial agents and/or biologically active materials, eitherbecause the tipping agent will not adhere properly or because themethodology (such as melt fusing) results in deterioration of thesuture, its coatings, additives, and fillers.

The suture tipping agent and method of the present invention arecompatible with and may be used on any type of surgical suture includingmultifilament bioabsorbable or non-bioabsorbable sutures.Advantageously, the tipping agent and method of the invention areapplicable to all types of multifilament braided sutures, includingthose which contain one or more fillers, coatings, etc.

In practice, a segment of the suture is selected for tipping and may beof any length appropriate for inserting a suture end cut from suchsegment into an opening, such as the barrel end of a surgical needle, tofacilitate attachment of the suture to the needle.

Typically the suture is placed under sufficient tension to take upslack. Additional tension may be applied to reduce the suture diameter,if desired, to result in a tipped section of reduced diameter relativeto the remainder of the suture.

A stiffening or "tipping" agent is then applied to the selected segmentof suture. The stiffening agent is a cyanoacrylate monomer such asmethyl 2-cyanoacrylate, or ethyl 2-cyanoacrylate. The preferredcyanoacrylate is available under the name LOCTITE(TM) Medical DeviceAdhesive 18014 and is available from the Loctite Corporation, 705 N.Mountain Road, Newington, Conn. 06111. The preferred Loctite MedicalDevice Adhesive is a moisture activated polymer which comprises 99+%ethyl cyanoacrylate and small amounts of hydroquinone and organicanhydride. It has a specific gravity of 1.05, and a boiling pointgreater than 300° F. The cyanoacrylate monomer may be applied in avariety of ways, such as dipping or brushing and preferably is appliedby spraying, as described below. Upon contact with the suture, theresidual moisture of the suture and surrounding environment catalyzesthe polymerization of the cyanoacrylate almost instantly. Thepolymerized cyanoacrylate stiffens the segment of the suture by coatingthe individual filaments of the suture with a relatively stiff coating,and, because the cyanoacrylate is an adhesive, the individual filamentsare bonded together to prevent brooming. A further advantage of theethyl cyanoacrylate tipping agent is that it is bioabsorbable and willnot leave a permanent residue in body tissue. Because the cyanoacrylatepolymerizes almost instantly, the tipping agent is stiffened immediatelywithout any additional drying or curing steps. This has the addedadvantage of reducing processing steps and accompanying handling andequipment requirements. In the preferred spray tipping process,polymerization is substantially complete by the end of the apparatuscycle and the tipped suture may be further processed without delay.

The next step is cutting the stiffened segment to create at least one"tipped" end for connecting to the end of a surgical needle. Two tippedends of the suture may be desirable for attaching a needle to each endof the suture to provide a so-called double armed suture. The coatedsegment may be cut with scissors, a razor blade, or by a knife edgemoving transverse to the direction of the tipped suture segment, or byany other suitable means.

Suture-Needle Attachment

The tipped end is now ready to be connected to the surgical needle.

One method of connection, illustrated in FIG. 1, requires a needle 1with a barrel end having an axial aperture 1a. The tipped end of suture2 is inserted into the aperture 1a and the end of the needle may then beswaged, crimped or otherwise constricted to grip and hold the suture,either permanently or with a pull-out force defined by U.S.P. fordetachable needles. The swage or crimp method of attachment isconventional and well known in the art.

Another method of attaching the suture to the needle is illustrated inFIG. 2 wherein the barrel end of the needle 1 has a cylindrical portion1b of lesser diameter than the needle and extending axially from theneedle 1. The "tipped" or stiffened end 2a of suture 2 is positionedadjacent portion 1b and extends axially through the bore of a tube 3,which is positioned around the junction of tipped end 2a and needleportion 1b. Tube 3 is made of a material capable of shrinking orundergoing contraction upon application of energy, e.g., heat. Suitablematerials include "memory based metals, " e.g , nickel-iron-titaniummixtures, or copper based materials, as are well known in the art (see,e.g., U.S. Pat. Nos. 3,759,552, 3,801,954, 4,198,081 and 4,733,680), andshrinkable plastic materials, such as polyvinylidene fluoride materialsavailable from Raychem Corporation, Menlo Park, Calif. under thetradename Kynar. One such polyvinylidene fluoride material availablefrom Raychem Corporation is RT-850. In the case of shrinkable plasticmaterials, the tubing typically is extruded such that the inner diameteris less than the final desired diameter, i.e., the inner diameter of thetubing after energy application in the attachment method of the presentinvention. Thereafter, the extruded tubing is expanded radially outwardthrough radial expansion means to provide a tubing or expanded innerdiameter. Such plastic tubing is thus adapted to shrink or "recover" toits original extruded inner diameter in response to the application of apredetermined amount of energy. Suitable energy sources to accomplishshrinking of tubing 3 include heat (convective or conductive),radiation, microwave energy, etc.

Tube 3 is then subjected to energy, preferably consisting of heat, inorder to cause shrinkage or contraction of the tube such that the innersurface of the tube bore grips both the needle portion 1a and the sutureend 2a in the vicinity of the joint as shown in FIG. 3. Alternatively,the tube may be attached to the needle and suture sequentially, such asby first applying localized energy to shrink the tube onto the needleshank and thereafter applying energy to the remainder of the tube toshrink the tube into the suture tip. Variations in the needle shank,such as tapering, contouring or ribbing, may be used to increasegripping force of the tube to the needle. Similarly, the relativegripping force of the tube on the needle shank and suture may be variedby varying the length of the tube section contacting each of the needleshank and suture. In addition, tube 3 preferably is configured anddimensioned such that When it is contracted the outer surface of thetube is substantially flush or even with the outer surface of theneedle. The gripping force of the shrinkable tube 3 is sufficient tomaintain the minimum required pull out force for the suture, and may beadjusted to provide either permanently attached or detachable sutureneedles. It has been found that sutures, particularly coated and filledsutures, tipped in accordance with the method of the present inventionhave significantly higher pull out forces.

Attempts were made to tip coated sutures, such as silicone coatedDacron® braided sutures, with polyurethane and epoxy adhesives. Theseattempts did not result in any tipped sutures suitable for attachment toneedles.

Comparative Examples 1-2

Dacron® polyester 1-0 braided sutures coated with silicone were tippedby swab application of (i) Arrochem composition; and (ii) a "hot melt" 010% paraffin/hexane solution. Sutures tipped with the 10%paraffin/hexane were further treated for 60 seconds in a heatingapparatus set at 315° F. The 10% paraffin/hexane solution was difficultto work with since it had to be maintained at about 130° F. withconstant stirring in order to maintain the paraffin in solution. Thetipped sutures were swaged to needles in a conventional manner andpull-out force in both cases was measured to be about 0.05 kg.

Comparative Example 3

In an attempt to improve on the results of Comparative Examples 1-2,Dacron® polyester 1-0 braided sutures were placed in toluene and broughtto temperature of 80°-82° C. for ten minutes. The total dwell time intoluene was approximately 20 minutes. The washed sutures were tippedwith 10% paraffin/hexane by swab application and heated to 315° F for 60seconds. The maximum pull-off forces were approximately 0.05 kg, showingno improvement.

Comparative Examples 4-14

Dacron® polyester 1-0 braided sutures coated with silicone wereultrasonically washed for five minutes in one of isopropyl alcohol,TP10, Freon TF, hexane, xylene, and III-trichloromethane. Samples ofsutures washed by each method were tipped with Arrochem solution and 10%paraffin/hexane (the paraffin/hexane tipped sutures were heated to 315°F. for 60 seconds, as before), resulting in twelve types of differentlytreated and tipped sutures. The tipped sutures were swaged to needlesand the pull-out force was measured. The pull-out forces of thesesutures showed some improvement, having pull-out forces of about 1.5 kg,but still did not achieve reliably high pull-out forces.

Comparative Examples 15-16

Silicone coated Dacron® polyester 1-0 braided sutures were wound on apaddle and soaked for five minutes in a 5% Mariotte mixture solution (50grams nylon in 946 ml. isopropyl alcohol and 150 ml. water). Thereafter,the sutures were heated for 60 seconds at 315° F. and, after cooling,Arrochem solution was applied over the tip previously treated withMariotte mixture. No improvement in pull out force was obtained, and theextended exposure to Mariotte mixture was observed to have detrimentaleffects on the suture braid.

The above procedure was repeated using a 10 minute soak in Mariottemixture followed by heat treating for 10 minutes in an oven at 225° F.followed by tipping with Arrochem composition. No improvement inpull-out force was observed when these sutures were attached to needles.

Comparative Example 17

Silicone coated Dacron® polyester 1-0 braided sutures wereultrasonically washed for 5 minutes in toluene and tipped with 10%paraffin/hexane solution by swab application. The pull-off force metU.S.P. minimums, e.g. 0.45 kg, but was still insufficient.

Comparative Examples 18-29

Silicone coated Dacron® polyester 1-0 braided sutures wereultrasonically washed for 10 minutes in a variety of different washingsolutions, tipped by soaking for 5 minutes in either Arrochem or 5%Mariotte mixture, and attached to needles. The results are listed belowin Table I.

                  TABLE I                                                         ______________________________________                                                                     Pull-Off                                         Cleaning Solution                                                                             Tipping Agent                                                                              Force (kg)                                       ______________________________________                                        18. Isopropyl alcohol                                                                         Arrochem     0.05-1.0                                         19. Isopropyl alcohol                                                                         Paraffin/Hexane                                                                            0.05-1.0                                         20. Freon T-F   Arrochem     0.05-1.0                                         21. Freon T-F   Paraffin/Hexane                                                                            0.05-1.0                                         22. Freon TP 10 Arrochem     0.05-1.0                                         23. Freon TP 10 Paraffin/Hexane                                                                            0.05-1.0                                         24. Trichloroethylene                                                                         Arrochem     0.05-1.0                                         25. Trichloroethylene                                                                         Paraffin/Hexane                                                                            0.05-1.0                                         26. Xylene      Arrochem     0.08-1.3                                         27. Xylene      Paraffin/Hexane                                                                            0.08-1.3                                         28. Hexane      Arrochem     0.08-1.3                                         29. Hexane      Paraffin/Hexane                                                                            0.08-1.3                                         ______________________________________                                    

Comparative Examples 30-33

Braided Dacron® polyester size 1-0 braided sutures were ultrasonicallywashed in a toluene bath for 20 minutes. After solvent cleaning thesutures were tipped by soaking for 5 minutes in one of (i) 10% SilasticMedical Adhesive in hexane; (ii) 10% paraffin/hexane; (iii) Arrochemsolution; or (iv) Mariotte mixture. All the tipped sutures werepost-tipped at 315° F. for 60 seconds. The tipped ends were cut andinserted into surgical needles, the needles were swaged, and the pullout forces were measured. The results are set forth in Table II.

                  TABLE II                                                        ______________________________________                                        Pull-out forces for Dacrone ® polyester 1-0 braided                       sutures ultrasonically cleaned in toluene for 20 minutes.                     Tipping Agent    Pull-out Force kg                                            ______________________________________                                        30.     Silastic/Hexane                                                                            1.0-1.8                                                  31.     Paraffin/Hexane                                                                            1.0-1.6                                                  32.     Arrochem     1.3-1.8                                                  33.     Mariotte Mixture                                                                           1.8-2.5                                                  ______________________________________                                    

From the foregoing it would appear that ultrasonic washing in toluene of20 minutes prior to tipping with a conventional agent might lead toacceptable results. Unfortunately, however, toluene is an undesirablematerial due to its toxicity and the harsh effects on the suturematerial.

Examples 1-6

Samples were selected for testing of (i) size 0 braided syntheticabsorbable sutures made from 90% glycolide, 10% lactide coated with aglycolide/lactide/polyethylene oxide mixture, and filled withglycerin/calcium lactate; and (ii) braided nylon (non-bioabsorbable)sutures coated with silicone lubricant. Selected segments of the sutureswere tipped with Loctite Selected segments of the sutures were tippedwith Loctite Adhesive 18014, which was allowed to fully polymerize. Thesuture segments were cut to create tipped ends which were then insertedinto a drilled hole in the barrel end of surgical needles. The needleswere then swaged by a) double hit swaging, b) split-ring, and c) cloverleaf dies, and pull out forces for each type of attachment weremeasured. Further information regarding split-ring and clover leafswaging may be found in U.S. patent application Ser. Nos. 07/431,303 and07/431,306 both filed Nov. 3, 1989. The test results are set forth inTables III, IV and V below.

                                      TABLE III                                   __________________________________________________________________________    Cyanoacrylate-Tipped Sutures                                                  Conventional Double-Hit Swaging                                                               PRE-STERILIZATION                                                                            POST-STERILIZATION                                             PULL-OUT FORCE PULL-OUT FORCE                                 SUTURE      SIZE                                                                              SAMPLES                                                                             AVG.                                                                              RANGE                                                                              SAMPLES                                                                             AVG.                                                                              RANGE                                __________________________________________________________________________    1. Synthetic Absorbable*                                                                  0    n-5  2.6 kgs.                                                                          --    n-5  2.9 kgs.                                                                          --                                   2. Braided Nylon**                                                                        0   n-10  1.8 kgs.                                                                          --   n-10  1.8 kgs.                                                                          --                                   __________________________________________________________________________

                                      TABLE IV                                    __________________________________________________________________________    Cyanoacrylate-Tipped Sutures                                                  Split Ring Swaging                                                                            PRE-STERILIZATION                                                                            POST-STERILIZATION                                             PULL-OUT FORCE PULL-OUT FORCE                                 SUTURE      SIZE                                                                              SAMPLES                                                                             AVG.                                                                              RANGE                                                                              SAMPLES                                                                             AVG.                                                                              RANGE                                __________________________________________________________________________    3. Synthetic Absorbable*                                                                  0   n-15  3.2 kgs.                                                                          2.9-3.7                                                                             n-8  3.1 kgs.                                                                          2.5-3.4                                                        kgs.           kgs.                                 4. Braided Nylon**                                                                        0   n-11  3.3 kgs.                                                                          1.4-7.1                                                                            n-15  2.9 kgs.                                                                          2.4-3.2                                                        kgs.           kgs.                                 __________________________________________________________________________

                                      TABLE V                                     __________________________________________________________________________    Cyanoacrylate-Tipped Sutures                                                  Clover Leaf Swaging                                                                           PRE-STERILIZATION                                                                            POST-STERILIZATION                                             PULL-OUT FORCE PULL-OUT FORCE                                 SUTURE      SIZE                                                                              SAMPLES                                                                             AVG.                                                                              RANGE                                                                              SAMPLES                                                                             AVG.                                                                              RANGE                                __________________________________________________________________________    5. Synthetic Absorbable*                                                                  0   n-15  3.5 kgs.                                                                          2.8-4.4                                                                             n-15 3.3 kgs.                                                                          2.5-4.1                                                        kgs.           kgs.                                 6. Braided Nylon**                                                                        0   n-15  2.9 kgs.                                                                          1.5-3.9                                                                            n-15  3.2 kgs.                                                                          1.9-4.1                                                        kgs.           kgs.                                 __________________________________________________________________________     *Synthetic Absorbable Sutures (90% glycolide/10% lactide) coated with wit     a glycolide/lactide/polyethylene oxide copolymer and filled with              glycerine/calcium lactate mixture                                             **Braided Nylon Sutures coated with silicone lubricant.                  

The minimum pull out force required by the U.S. Pharmacopeia for size 0suture is 1.5 kg Avg/0.45 kg individual. As can be seen from Tables III,IV, and V, the pull out forces for the cyanoacrylate tipped suturesexceeds the minimum USP requirements.

As can be seen from a comparison of the pull-out forces tabulated in theabove examples and comparative examples, the suture tipping method ofthe present invention using cyanoacrylate tipping agent producespull-out forces superior to those of methods using prior known tippingagents, particularly with respect to filled sutures and sutures coatedwith lubricant coatings. Remarkably, these results are attained withoutwashing the suture prior to cyanoacrylate tipping. This is surprisingsince the prior known methods of using cyanoacrylates typically requirethe surface to be bonded to be free of oils, mold release agents, orother foreign matter in order to achieve maximum bond performance.

Tipping Apparatus

The following description discloses the preferred apparatus for sprayingcyanoacrylate monomer onto the suture by atomization.

Method For Winding A Suture

To insure consistency of the diameter at the tipped portion of thesuture, a method and apparatus have been developed for monitoring sutureovality and adjusting winding tension to control and, if desired, modifythe suture diameter. A diagram of the system for loading sutures on adrum is illustrated in FIG. 4.

The pay off section includes a spool 10 on which suture material 11 isstored. A friction tensioning device applies drag to the outside of thespool to prevent the spool from freewheeling. The suture is guided ontoa capstan 12 which is electronically controlled by means of frictionclutch 13 and clutch power supply 14. The suture 11 then passes onto thedrum assembly 26. Power is supplied by standard 120 volt power sources15. When tension is applied to the suture, the suture diameter isreduced. When the clutch is relaxed, the diameter of suture materialunder tension expands. Based on dimensional information continuously fedto the clutch control from an x-y laser micrometer 18, the clutchapplies tension to or releases the suture in order to maintain suturediameter within selected parameters.

The x-y laser micrometer 18 continuously monitors the diameter of thesuture in the x and y directions, i.e. suture ovality, by means of x-yheads 19 which are oriented orthogonal to each other. The lasermicrometer electronically compares the x-y measurements with preselectedminimum and maximum dimensions pertaining to the particular type andsize of suture. This information is employed in a negative feedbackcontrol loop whereby the clutch tension is adjusted by means of a drivemotor 17 and potentiometer clutch controller 16. In the event eitherdimension exceeds the maximum diameter for the suture size, the clutchtension is increased in order to decrease the diameter of the suture. Inthe event either dimension is less than the minimum suture diameter theclutch tension is relaxed until the suture diameter is increased intothe suture diameter range. The information is processed and clutchtension adjusted within milliseconds of the actual measurement tocontinuously adjust clutch tension.

Referring more specifically to the laser micrometer, an instrumentsuitable for use in the present invention is available from ZumbachElectronics Corp., 140 Kisco Avenue, Mount Kisco, N.Y. 10549 under thedesignation ODAC 19M, which is a microcomputer controlled measuringsystem having x-y heads which incorporate laser scanners.

FIG. 5 illustrates a side view of the suture handling apparatus. Suturestorage spool 10 is rotatably mounted at the top of mounting frame 20.Suture 11 is drawn off and passes through guide 21, around capstan 12and over and around guide roller 22. Suture 1 then passes through asecond guide member 23, through laser micrometer 18 where the x-ymeasurements are made, around guide rollers 24 and 25, and finally ontodrum 26. Drum 26 is mounted onto drum mounting frame 27 and is driven toreceive suture 11 and maintain tension thereon. During winding of thesuture onto drum 26, drum mounting frame 27 traverses in the planeperpendicular to FIG. 5 so that the suture is continuously wound aroundthe drum in a helix from one end of the drum to the other with no twoadjacent suture portions touching.

FIGS. 6 and 7 illustrate the drum assembly 26 in greater detail.

Referring to FIG. 6, the drum assembly comprises a substantiallycylindrical drum 26 having a smooth circumferential surface 31. In orderto facilitate gentle treatment of the sutures, the drum may be made ofpolished stainless steel or stainless steel covered with a siliconrubber skin. Most preferably, drum 26 is fabricated from high densitypolyethylene with steel end plates. High density polyethylene has beenfound to be particularly advantageous since excess cyanoacrylate doesnot adhere to this material during the tipping operation. Where the drumis constructed of high density polyethylene it further has been founddesirable to reinforce the drum against deformation by providing aplurality of gussets or ribs inside the drum. An end view of oneappropriate rib configuration is shown in FIG. 6A. Each rib has athickness of about 1/4 to 3/4 inches in the direction perpendicular tothe plane of FIG. 6A. The number of ribs may vary, but two to five ribsshould be appropriate, and three ribs are preferred. Drum 26 could alsobe fabricated from a solid block of high density polyethylene, but theadded weight of such a construction most likely will not be desired.

Referring again to FIG. 6, a notch 32 extends lengthwise along the drum.When suture 11 is wound around the drum a portion of each suture wrapwill extend across the notch orthogonally to the lengthwise orientationof the notch. The end plate 33h has central apertures 34 and an axialspindle 29 by which the drum can be mounted to fixture 27 such that thedrum can be rotated to wind suture 11 thereon. Apertures 35 and 36 arefor mounting the suture retainer clamps to hold the tipped sutures inplace while the tipped section is cut to remove the sutures from thedrum, as described below. Peripheral apertures 37 are for attachment ofthe end plates to the drum, such as by screw mounting, and aperture 38is provided to receive a positioning pin on the tipping apparatus tohold the drum in the correct orientation during tipping. Of course,drums of different circumference can be made in order to provide tippedsutures of different lengths. By way of example only, drums having acircumference of thirty six, thirty, twenty four and eighteen inches arecontemplated. The cylindrical construction of the drum has the addedadvantage of being conducive to providing multiple longitudinal notcheson drums of different circumference in order to be able to tip a varietyof different length sutures in a single tipping operation. FIGS. 6B and6C show end elevational views of drums 26B and 26C having 2 and 3notches, 32, respectively. It is contemplated that drums having thefollowing general dimensions (inches) could be provided.

    ______________________________________                                        Drum           Number    Tipped                                               Circumference  of Notches                                                                              Suture Lengths                                       ______________________________________                                        15             3         5                                                    16             2         8                                                    24             2         12                                                   ______________________________________                                    

Spray Tipping Apparatus

The present invention contemplates tipping a suture by passing theportion of the suture to be tipped through a mist or cloud of rapidlycuring material, such as the cyanoacrylate monomer described above. Thecyanoacrylate monomer is absorbed into the suture braid matrix andusually cures almost immediately. Misting of the cyanoacrylate monomeris achieved by passing it through an atomization nozzle which atomizesthe liquid monomer by means of sonic/ultrasonic vibration. The tippingprocess is described more fully as follows.

After the suture 11 has been wound on drum 26, the drum may betransferred to an apparatus 100 for tipping the suture. Such anapparatus is illustrated in FIGS. 14, 15, and 16, which are now referredto. Drum assembly 26 with suture 11 wound thereon is mounted onto drummounting carriage 110 in the loading chamber 101 of the suture tippingapparatus 100. Drum mounting carriage 110 has twin uprights 111, eachupright having a drum support plate with notches 112a for receivingspindles 29 of the drum. Mounting carriage 110 also has a base 113 witha lower member 114 for slidably engaging rail 120 which extendslongitudinally from the loading chamber 101 to the processing chamber102. The loading chamber 101 may be accessed by means of cover panel 103which can be pivoted upward to open the loading chamber 101. The tippingapparatus further includes a control panel 130, window 104, soniccontrol unit 140, liquid storage and transmission system 150, meteringcontrol system 170, exhaust port 190 (FIG. 16) for removing vapors oftipping agent and solvents, and a spray head assembly 160. The liquidstorage system 150 includes solvent reservoir 213 and tipping solutionreservoir 212 and associated transmission lines as discussed below withreference to FIG. 20. A plenum member 105 connected to a source ofvacuum extends longitudinally within processing chamber 102 to a pointbelow the spray head assembly 160. Plenum 105 is supported by plenummount 106, which is braced by gusset 106a. Long and short manifolds 107and 108, respectively, are below base 109.

At the top of the unit 100 the sonic control unit 140 is asonic/ultrasonic frequency signal generator. The signal is sent to theatomizer nozzle 161 of spray head assembly 160 described below. Atomizernozzle 161 is the outlet for the tipping solution which creates a finemist for spraying the suture. The electric signal from sonic controlunit is transmitted by conductive wire to piezoelectric elements in theatomizer nozzle. A fluid passing through the nozzle is thereby atomizedinto a fine mist.

A device suitable for use as the sonic control unit 140 in the presentinvention is manufactured by Sono-Tek Corporation of 313 Main Mall,Poughkeepsie, N.Y.

The advantage to using sonic/ultrasonic atomization as opposed topressurized spray is that lower flow velocities may be used. Thiseliminates bounceback of the sprayed material from the workpiece, whichis a problem with pressure spraying. Another advantage ofsonic/ultrasonic atomization over pressure atomization is that theoutlet orifice diameter of the sonic/ultrasonic atomizer nozzle can berelatively wide while still providing a suitable mist of tipping agent.This helps prevent clogging of the orifice.

Yet another advantage is that the atomization creates a cloud or mistwhich, when the suture is passed through, coats and saturates all sidesof the suture, not just the side of the suture facing the outlet orificeof the atomizer. Thus, the application of tipping agent is not limitedby line of sight impingement of tipping agent onto the suture, as wouldbe the case with simple spray application.

Referring now to FIGS. 17 and 18, the spray head assembly 160 includesspray nozzle 161, which comprises a downwardly projecting member 161ahaving an internal bore 161h terminating in orifice outlet 161g. Thecyanoacrylate tipping agent passes through said bore and is atomized toa fine mist 164 upon exiting the nozzle. Atomization is achieved bymeans of piezoelectric elements 161b and 161c which are electricallyconnected via wires 161d and 161e respectively to the Son-Tek signalgenerating unit 140. The signals from the unit 140 may be varied infrequency to adjust the fineness of the mist. O-rings 161f provide aseal for the atomization nozzle 161.

Blocks 162 have an internal chamber for an inert gas such as nitrogen,which is fed in through gas line 163. The gas exits via apertures 162bin the bottom of the blocks 2.

Plenum member 105 has an aperture 105a positioned below the atomizernozzle 161 so as to catch any excess spray. The aperture also permitsthe suture to be surrounded by the mist so that the entire suture,including the underside of the suture, is uniformly coated with thecyanoacrylate monomer.

FIG. 20 is a schematic flow chart of the tipping system. Gas supply 219is a source of inert gas, preferably nitrogen. Optionally, a source ofcompressed air may be provided with air being fed to the ports betweentipping cycles, i.e. when the instrument is not being used. Nitrogen issent to five port manifold 201 where it is distributed by regulators 210at each port to the various parts of the system. Line 201a isdistributed through 3-way valve 204 to spray ring 217. Optional switch224 activates the optional supply of air to the ports when the tippingapparatus is inactive. Line 201b is distributed through 2-way valve 207and two 3-port flow through 206 to the ultrasonic atomization nozzle 160for blowing through the orifice 161g in a clearing procedure. Line 201cis distributed to the solvent reservoir 213 for pressurization.

Line 213a from the solvent reservoir carries solvent such as acetone,methylethylketone, or preferably 1,1,1-trichloroethane. The solvent isused to flush residual cyanoacrylate tipping agent from the system. Line201d carries nitrogen through 3-way valve 204 to the inert gas chamber162. Line 201e carries nitrogen through metering system 170 andregulator 210 to pressurize the tipping agent storage bottle 212. Thetipping agent is carried via line 212e through 3-port flow through 206to the atomizing nozzle 160 where it is misted and sprayed onto asuture.

Pressurized air is sent to 2-port manifold 202 and carried via line 202athrough regulator 210 and 3-way valve 204 and 4-way valve 205 to lowerthe carriage drive 214 from moving the drum mounting carriage 10.Compressed air is also sent via line 202b through a regulator 210 to amechanism 215 for opening and closing cover panel 103.

The tipping procedure is as follows. A drum assembly 26 with suture 11wound thereon is placed onto the drum mounting carriage in the loadingchamber 101 of the apparatus (See FIG. 14). The cover panel 103 isclosed and the tipping sequence is initiated on the control panel 130.Compressed air powers the carriage drive 214 to move the carriage 110and drum assembly into the processing chamber 102. As drum 26 enterschamber 102, plenum member 105 becomes disposed in notch 32 beneath thesuture. As the drum assembly 26 moves under the spray head assembly 160,pressurized nitrogen at 2 psi enters the tipping solution supply tobottle 212 and moves the tipping agent to the nozzle 161 where it isatomized by sonic or ultrasonic frequency generated by the Sono-Tek unit140. Generally a frequency of about 60 cycles is preferred althoughother frequencies may be selected. The tipping agent is atomized tocreate a cloud or mist 164 (See Figs. 7 and 8) which envelopes thesutures as they pass underneath during the traverse of drum 26 intochamber 26. Only those portions of the suture traversing the notch 32are coated with tipping agent. As the sutures sequentially pass throughthe mist of tipping agent they are saturated with the agent which beginsto cure in a very short period of time, typically in less than a second.The cyanoacrylate cures by polymerization catalyzed by ambient moisture.While the tipping agent is being sprayed nitrogen is blown throughapertures 162b of inert gas chambers 162 to create a "curtain" ofnitrogen gas which blows excess tipping agent from the suture 11 intoplenum 105 to be drawn off under vacuum.

On the return pass of drum 26 from chamber 102 to chamber 101 the sutureagain passes underneath the nozzle and, optionally, an additionaltipping application can be made during this pass. Alternatively, severalpasses back and forth underneath the nozzle can be made to apply tippingagent several times. When the procedure is completed, the drum supportcarriage returns to the loading chamber 101, and solvent from reservoir213 is flushed through the system to clear out residual tipping agent.Thereafter, nitrogen is flushed through the atomizing head to clear outany residual solvent.

The tipping agent is preferably a solution of ethylcyanoacrylate monomerin methylethylketone (MEK). Approximately 250 milliliters of MEK isadded to 8 ounces of ethylcyanoacrylate to adjust the viscosity of thetipping agent to a range of from about 2 to 3 centipoise. Methylenechloride is also an acceptable solvent.

Alternatively various other materials can be added to the tippingsolution. For example, an bioabsorbable copolymer of glycolide andlactide may be dissolved in the tipping solution to form a biodegradablecoating on the suture braids. If such an additive is employed the amountof MEK may have to be adjusted to keep the viscosity of the tippingsolution within a range of about 2 to 3 centipoise. Too high a viscositymakes atomization of the tipping agent more difficult, and inhibitswicking or absorption of the tipping agent into the filaments of thebraided suture. Referring to FIG. 19, the tipped portion 11a of suture11 is usually fully polymerized and dried in about 20 to 30 seconds.

Cutting The Tipped Sutures From The Drum

After the tipping solution has polymerized, the tipped suture may beremoved from the drum by cutting the tipped suture, such as with ascissors or by passing a razor or knife blade across the tipped portionto create suture segments having two tipped ends suitable for use inconjunction with a surgical needle as explained above with reference toFIGS. 1 to 3.

In order to facilitate controlled cutting and removal of the tippedsutures from the drum, removable drum clamps are provided to be mountedonto the drum after tipping is complete.

A drum clamp 40 is illustrated in side view in FIG. 7. As explainedbelow, suture clamp 40 is mounted to drum 26 after the suture 11 hasbeen tipped in order to retain the suture in place during removal of thesuture from the drum. Suture clamp 40 includes a main support 41 whichis a U-shaped elongated member having mounting apertures 41a, asillustrated in FIG. 8. Referring again to FIG. 7, suture clamp 40 alsoincludes dowel arm support 42 as illustrated in perspective view in FIG.9. Dowel arm support 42 has dowel apertures 42a for receiving dowels 48which provide means for mounting the dowel support arm to the mainsupport 41. At least one aperture 42b on the dowel arm support acceptsbutton screw 49a for mounting dowel arm 43 to dowel arm support 42a.

Referring additionally to FIG. 10, dowel arm 43 includes an elongatedaperture 43a through which button screw 49a extends for mounting toaperture 42b on the dowel arm support. Aperture 43b retains dowel 47 formounting into aperture 35 of drum 26, as will be explained below.

Suture clamp 40 further includes a rocker clamp support 44 shown inFIGS. 7 and 11, which includes a knurled portion 44a, an aperture 44bfor accepting a button screw 49b for mounting a rocker clamp 45, anaperture 44c for receiving a dowel 48 for mounting to main support 41,and another aperture (not shown in FIG. 11) for receiving a button screw49c for mounting rocker spring 46 to the rocker clamp support (See FIG.7).

Referring now to FIG. 12, rocker clamp 45 includes an elongated aperture45a for receiving button screw 49b for mounting the rocker clamp torocker clamp support 44. The downwardly extending leg portion of rockerclamp 45 includes a hook 45b for mounting into an elongated aperture 36in the drum, in a manner to be described below.

Referring to FIGS. 7 and 13, a rocker spring 46 mounts to the undersideof rocker clamp support 44 by means of button screw 49c which extendsthrough aperture 46a and into a receiving aperture in the rocker clampsupport 44.

The undersurface of the suture clamp 44 comprises a layer of softresilient material 50 for contacting the suture and holding the sutureto the surface of the drum 30. The preferred material for layer 50 is asilicone rubber material available from CHR Industries, New Haven,Conn., under the designation COHRlastic 9275. The material is preferablyof low modulus (soft). The thickness of the foam can range from about 30to 500 mils and is preferably about 100 to 150 mils.

In use, after suture material 11 is wound onto drum 26 on windingapparatus 20 and the sutures have been tipped, such as by tippingapparatus 100, a pair of suture retaining clamps 40 are mounted to thedrum on either side of notch 32 extending longitudinally parallelthereto, as illustrated in FIG. 21. The clamps are mounted in oppositeorientation to one another, and are mounted by engaging dowel 47 intoaperture 35 of drum 26 (see FIGS. 6 and 7a), and thereafter engagingrocker clamp hook 45b in elongated slot or aperture 36 on the drum. Hook46b is biased by spring 46 into engagement with elongated slot 36. Withclamps 40 mounted on either side of notch 32, the tipped suture segmentcan be cut by knife 200 down the longitudinal length of notch 32.Because clamps 40 retain each end of the cut suture against the drumadjacent to the notch, the sutures do not fall uncontrolled away fromthe drum. After the suture has been cut, knurled portion 44a is pressedto overcome spring 46 and release hook 45b from slot 36, therebyreleasing the cut sutures from the drum in a controlled manner.

It is also contemplated that clamps 40 could be mounted onto drum 26prior to tipping and remain in place during tipping of the sutures andremoval of the tipped sutures from the drum.

What is claimed is:
 1. In a needle suture combination which comprises asurgical needle having a bore at one end, and a surgical suture havingan end inserted into said bore and retained therein by swaging appliedto said needle in the vicinity of said bore the improvement comprisingsaid end of said suture tipped by application thereto of a cyanoacrylatecompound which is substantially fully cured prior to insertion of saidend of said surgical suture into said aperture of said surgical needle.2. In a needle-suture combination, which comprises:a) a needle having abarrel end with a longitudinally extending bore; and b) a multifilamentsuture coated with a lubricant material, said coated suture having alubricant-containing end portion inserted into said needle bore andretained therein in response to a swage applied to said needle in thevicinity of said bore, the improvement comprising saidlubricant-containing end portion tipped by a cyanoacrylate tipping agentwhich is substantially fully cured prior to insertion of said lubricantcontaining end portion into said needle bore.
 3. The needle-suturecombination of claim 2 wherein said multifilament suture is a syntheticbioabsorbable suture.
 4. The needle-suture combination of claim 3wherein said multifilament synthetic bioabsorbable suture is fabricatedfrom a material selected from the group consisting of polymers ofglycolide, lactide, dioxanone, caprolactone, trimethylene carbonate, andphysical and chemical combinations thereof.
 5. The needle-suturecombination of claim 3, wherein said lubricant coating material is abioabsorbable coating composition obtained by copolymerizing(i) apolyether glycol corresponding to the general formula HO(RO)_(n) Hwherein R is an alkylene group of from 2-4 carbon atoms and n is aninteger of from about 100-350, and polyethylene oxide-polypropyleneoxide block copolymer, corresponding to the general formula H(OCH₂CH₂)_(x) (OC₃ H₆)_(y) (OCH₂ CH₂)_(z) OH wherein x is an integer of fromabout 45-90, y is an integer of from about 60-85 and z is an integer offrom about 45-90, with (ii) a mixture of lactide monomer and glycolidemonomer or a preformed copolymer of lactide and glycolide, the weightratio of (i) to (ii) ranging from about 4:1 to about 1:4 and the ratioof lactide to glycolide in (ii) varying from about 65-90 mole percentlactide and 10-35 mole percent glycolide.
 6. The needle-suturecombination of claim 2 wherein said multifilament coated suture isfilled with a storage stabilizing amount of a filling agent.
 7. Theneedle-suture combination of claim 6, wherein said filling agentcomprises glycerol.
 8. The needle-suture combination of claim 6, whereinsaid filling agent is selected from the group consisting of a watersoluble polyhydroxy compound, and ester of a water soluble polyhydroxycompound, and mixtures thereof.
 9. The needle-suture combination ofclaim 8, wherein said polyhydroxy compound is selected from the groupconsisting of glycerol, ethylene glycol, diethylene glycol triethyleneglycol, 1,3-propanediol, trimethylolethane, trimethylolpropane,pentaerythritol, and sorbitol, and said ester of said polyhydroxycompound is selected from the group consisting of glycerol monacetateand glycerol diacetate.
 10. The needle-suture combination of claim 9,wherein said filling agent includes a thickener.
 11. The needle-suturecombination of claim 10, wherein said thickener comprises a compoundselected from the group consisting of hydroxypropylmethylcellulose, guargum, xanthan gum, gelatin, collagen, alkali and alkaline earth metalsalts of lactic acid, salts of glycolic acid, salts of 3-hydroxypropanoic acid, and salts of 3-hydroxybutanoic acid.
 12. A needle-suturecombination which comprises:a) a needle having a barrel end with alongitudinally extending bore; and b) a multifilament suture having anend portion , the end portion inserted into the bore and retained in thebore by a swage applied to the needle in the vicinity of the bore theimprovement comprising the end portion of the suture tipped withsubstantially fully cured cyanoacrylate.